Creating CloudWatch alarms - Amazon DynamoDB
Creating an alarm in the CloudWatch consoleCreating an alarm in the Amazon CLIMore Amazon CLI examples
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Creating CloudWatch alarms

A CloudWatch alarm watches a single metric over a specified time period, and performs one or more specified actions, based on the value of the metric relative to a threshold over time. The action is a notification sent to an Amazon SNS topic or Auto Scaling policy. You can also add alarms to dashboards so you can monitor and receive alerts about your Amazon resources and applications across multiple regions. There is not limit to the number of alarms you can create. CloudWatch alarms do not invoke actions simply because they are in a particular state; the state must have changed and been maintained for a specified number of periods. For a list of recommended DynamoDB alarms, see Recommended alarms.

Note

You must specify all the required dimensions when creating your CloudWatch alarm, since CloudWatch will not aggregate metrics for a missing dimension. Creating a CloudWatch alarm with a missing dimension will not result in an error, when creating the alarm.

Assume you have a provisioned table with five read capacity units. You want to be notified before you consume the entire provisioned read capacity, so you decide to create a CloudWatch alarm to get notified when the consumed capacity reaches 80% of what you have provisioned for the table. You can create alarms in the CloudWatch console or using the Amazon CLI.

Creating an alarm in the CloudWatch console

To create an alarm in the CloudWatch console

  1. Sign in to the Amazon Web Services Management Console and open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.

  2. In the navigation pane, choose Alarms, All alarms.

  3. Choose Create alarm.

  4. Find the row with the table that you want to monitor and ConsumeReadCapacityUnits in the Metric Name column. Select the check box next to this row and choose Select metric.

  5. Under Specify metric and conditions, for Statistic choose Sum. Choose a Period of 1 minute.

  6. Under Conditions, specify the following:

    1. For Threshold type, choose Static.

    2. For Whenever ConsumedReadCapacityUnits is, choose Greater/Equal and specify the threshold as 240.

  7. Choose Next.

  8. Under Notification, choose In alarm and select an SNS topic to notify when the alarm is in ALARM state.

  9. When finished, choose Next.

  10. Enter a name and description for the alarm and choose Next.

  11. Under Preview and create, confirm that the information and conditions are what you want, then choose Create alarm.

Creating an alarm in the Amazon CLI

aws cloudwatch put-metric-alarm \
    -\-alarm-name ReadCapacityUnitsLimitAlarm \
    -\-alarm-description "Alarm when read capacity reaches 80% of my provisioned read capacity" \
    -\-namespace AWS/DynamoDB \
    -\-metric-name ConsumedReadCapacityUnits \
    -\-dimensions Name=TableName,Value=myTable \
    -\-statistic Sum \
    -\-threshold 240 \
    -\-comparison-operator GreaterThanOrEqualToThreshold \
    -\-period 60 \                           
    -\-evaluation-periods 1 \
    -\-alarm-actions arn:aws:sns:us-east-1:123456789012:capacity-alarm

Test the alarm.

aws cloudwatch set-alarm-state -\-alarm-name ReadCapacityUnitsLimitAlarm -\-state-reason "initializing" -\-state-value OK
aws cloudwatch set-alarm-state -\-alarm-name ReadCapacityUnitsLimitAlarm -\-state-reason "initializing" -\-state-value ALARM

More Amazon CLI examples

The following procedure describes how you're notified if you have requests that exceed the provisioned througput quotas of a table.

  1. Create an Amazon SNS topic arn:aws:sns:us-east-1:123456789012:requests-exceeding-throughput. For more information, see Set up Amazon Simple Notification Service.

  2. Create the alarm.

    aws cloudwatch put-metric-alarm \
        -\-alarm-name ReadCapacityUnitsLimitAlarm \
        -\-alarm-description "Alarm when read capacity reaches 80% of my provisioned read capacity" \
        -\-namespace AWS/DynamoDB \
        -\-metric-name ConsumedReadCapacityUnits \
        -\-dimensions Name=TableName,Value=myTable \
        -\-statistic Sum \
        -\-threshold 240 \
        -\-comparison-operator GreaterThanOrEqualToThreshold \
        -\-period 60 \                           
        -\-evaluation-periods 1 \
        -\-alarm-actions arn:aws:sns:us-east-1:123456789012:capacity-alarm

  3. Test the alarm.

    aws cloudwatch set-alarm-state --alarm-name RequestsExceedingThroughputAlarm --state-reason "initializing" --state-value OK
    aws cloudwatch set-alarm-state --alarm-name RequestsExceedingThroughputAlarm --state-reason "initializing" --state-value ALARM

The following procedure describes how you're notified if you get system errors.

  1. Create an Amazon SNS topic arn:aws:sns:us-east-1:123456789012:notify-on-system-errors. For more information, see Set up Amazon Simple Notification Service.

  2. Create the alarm.

    aws cloudwatch put-metric-alarm \
    --alarm-name SystemErrorsAlarm \
    --alarm-description "Alarm when system errors occur" \
    --namespace AWS/DynamoDB \
    --metric-name SystemErrors \
    --dimensions Name=TableName,Value=myTable Name=Operation,Value=aDynamoDBOperation \
    --statistic Sum \
    --threshold 0 \
    --comparison-operator GreaterThanThreshold \
    --period 60 \
    --unit Count \
    --evaluation-periods 1 \
    --treat-missing-data breaching \
    --alarm-actions arn:aws:sns:us-east-1:123456789012:notify-on-system-errors

  3. Test the alarm.

    aws cloudwatch set-alarm-state --alarm-name SystemErrorsAlarm --state-reason "initializing" --state-value OK
    aws cloudwatch set-alarm-state --alarm-name SystemErrorsAlarm --state-reason "initializing" --state-value ALARM